This invention relates to electronic devices such as rotating disk data storage devices as typified by CD-ROM drives as incorporated particularly in laptop or notebook computers. More specifically, the invention pertains to a safety system for preventing the accidental overheating of an electric actuator in such electronic devices, an example of such electric actuator being a solenoid customarily used in a CD-ROM drive for unlocking the tray for ejection together with or without a CD-ROM disk loaded thereon.
The CD-ROM drive has found widespread use as a computer peripheral with the advent and ever-increasing commercial acceptance of CD-ROM databases, as disclosed for example in Fujimoto et al. U.S. Pat. No. 5,844,866. As incorporated specifically in a laptop computer, for example, the CD-ROM drive has a movable tray for carrying the optical disk into and out of the disk drive casing. Usually, the tray has mounted thereto an optical pickup assembly for reading the disk loaded on the tray, a disk drive motor for imparting rotation to the disk, and a pickup drive motor for moving the pickup assembly across the track turns on the disk. Together with all these components, as well as with the disk, if any, loaded thereon, the tray travels between a data transfer position within the disk drive casing, where the pickup assembly reads the disk in rotation on the tray, and a load/unload position where the tray is mostly exposed outside the casing for permitting the disk to be loaded thereon or unloaded therefrom.
A familiar example of means for causing such tray travel is an ejector spring biasing the tray from data transfer position toward load/unload position. The ejector spring is used in combination with a locking mechanism for locking the tray in the data transfer position against the bias of the ejector spring. Japanese Unexamined Patent Publication No. 7-235415 suggests use of a solenoid in the locking mechanism. The solenoid is left unenergized when the tray is in the data transfer position, permitting the locking mechanism to lock the tray in that position. Upon depression of an eject button on the front bezel of the CD-ROM drive casing, the solenoid is energized to cause the locking mechanism to unlock the tray, permitting the same to be spring ejected to the load/unload position.
Also as is well known, the CD-ROM drive incorporates a controller, which includes a central processor, for controlling the solenoid of the locking mechanism and various other working parts of the disk drive such as the disk drive motor and the pickup drive motor. The controlling of the various working components of the CD-ROM drive by the controller has had a problem left unsolved in conjunction with the solenoid of the tray locking mechanism.
Functioning normally, the controller causes the solenoid to be energized for tray ejection as aforesaid and to be deenergized immediately upon tray ejection. The solenoid is therefore energized only at the moment of tray ejection, being held deenergized when the tray is in either the data transfer or the load/unload position. No heat problem is to occur as a result of solenoid energization as long as the controller is functioning normally.
Let it be supposed, however, that the controller malfunctions for some reason or other and, as has been liable to occur heretofore, allows the solenoid to be kept energized even after tray ejection. The solenoid has then overheated, possibly damaging or destroying itself, the neighboring parts thereof, particularly those molded from plastics, and, of course, the disk which is vulnerable to heat, even though the disk together with the tray is now assumed to have been ejected and so to be positioned some distance away from the overheating solenoid.
This kind of trouble is not limited to CD-ROM drives. It can happen in other comparable electronic devices, such for example as magnetic disk drives and printers, having a solenoid or other electric actuators operating under the direction of a microcontroller.
The present invention seeks, in a CD-ROM drive and other electronic devices having an electric actuator to be energized and deenergized under the control of a controller, to protect the actuator from overheating as a result of energization for an extended period of time due to the malfunctioning of the controller.
The invention also seeks, in attaining the first recited object, to make utmost use of the preexisting parts of a CD-ROM drive or like electronic device and to make it proof against overheating of the actuator without any major alteration of the conventional mechanical construction or electric circuitry.
Briefly stated in its perhaps broadest aspect, the present invention concerns an electronic device having a stationary segment and a movable segment, the movable segment being movable relative to the stationary segment between a first and a second position. The invention particularly concerns, in such electronic device, the combination comprising drive means for moving the movable segment from the first toward the second position relative to the stationary segment, the drive means including electric actuator means which, when activated, at least causes the movable segment to start traveling from the first toward the second position. Also included are a sensor for sensing whether the movable segment is in the first position or not, and a controller for providing a signal for activating and deactivating the actuator means. The invention particularly features a protection circuit having an input connected to the sensor, another input connected to the controller, and an output connected to the actuator means, for permitting the controller to activate the actuator means only when the movable segment is in the first position.
Thus, even in the event of controller malfunctioning, the actuator means is not to be left energized after the movable segment has traveled away from the first toward the second position. There is accordingly no danger of the actuator means, or even the complete device, ruined by the overheating of the actuator means.
In the preferred embodiments of this invention to be disclosed subsequently, in which the invention is applied to a CD-ROM drive, the disk tray is the primary component of the movable segment, and the casing of the disk drive that of the stationary segment. The tray travels between a data transfer position within the casing and a load/unload position outside the casing. The electric actuator means comprises a solenoid to be energized and deenergized by a solenoid driver circuit under the direction of a controller. When energized, the solenoid unlocks the tray and so permits the same to travel from the data transfer toward the load/unload position under the force of an ejector spring. The protection circuit constituting a feature of this invention has two inputs connected to the controller and a tray sensor, and an output connected to the solenoid driver circuit, for permitting the driver circuit to energize the solenoid in response to an ejection command from the controller only when the tray is in the data transfer position.
The protection circuit takes the form of a simple OR gate in one embodiment, and an inhibit AND gate in another, depending upon whether the controller goes high or low for tray ejection. The invention is applicable to CD-ROM drives of known constructions merely by incorporating this simple protection circuit in their electric circuitry.
The above and other objects, features and advantages of this invention and the manner of achieving them will become more apparent, and the invention itself will best be understood, from a study of the following description and attached claims, with reference had to the accompanying drawings showing the preferred embodiments of the invention.